STAHL, Circuit Judge.
Following a lengthy criminal trial, a jury convicted defendant Alfred Trenkler
of various charges stemming from a bomb explosion in Roslindale, Massachusetts
("the Roslindale bomb"). On appeal, Trenkler challenges the admission of
evidence relating to his participation in a prior bombing that occurred
five years earlier in Quincy, Massachusetts ("the Quincy bomb"). Trenkler
also assigns error to two evidentiary rulings admitting evidence derived
from a computer database that purported to establish that Trenkler built
both the Quincy and the Roslindale bombs and several out-of-court statements
[**2] made by a fellow participant in the bombing. After careful review,
we affirm.

I.

Background

On October 28, 1991, a bomb exploded at the Roslindale home of Thomas
L. Shay ("Shay Sr."), killing one Boston police officer and severely injuring
another. The two officers, members of the Boston Police Department Bomb
Squad, had been dispatched to Shay Sr.'s home to investigate a suspicious
object located in Shay Sr.'s driveway. Shay Sr. had earlier reported that,
while backing his 1986 Buick Century into the street the day before, he
had heard a loud noise emanating from beneath the floorboard of his automobile.
Shay Sr. added that, subsequently, he found the suspicious object resting
near the crest of his driveway.

Following the explosion, a massive investigation ensued involving a variety
of federal, state and local law-enforcement agencies. On June 24, 1993,
this investigation culminated with the return of a three-count indictment
charging Trenkler and Thomas A. Shay ("Shay Jr."), Shay Sr.'s son, with
responsibility for the Roslindale bombing. Trenkler filed a successful
severance motion, and the government tried the two defendants separately.
Shay Jr. was tried first, and a jury convicted him on counts of conspiracy
and malicious destruction of property by means of explosives.

At Trenkler's trial, the thrust of the government's case was that Trenkler
had built the Roslindale bomb for Shay Jr. to use against his father.
To establish Trenkler's identity as the builder of the bomb, the government
offered, inter alia, evidence that Trenkler had previously constructed
a remote-control device, the Quincy bomb, which exploded in Quincy, Massachusetts,
in 1986. The government contended that unique similarities in design,
choice of components, and overall modus operandi between the two bombs
compelled the conclusion that Trenkler had designed and built both devices.
Prior to trial, the government filed a motion in limine seeking to admit
the "similarity" evidence. Following a day-long evidentiary hearing, the
district court ruled the evidence admissible, finding that it was relevant
on the issues of identity, skill, knowledge, and intent. Although Trenkler
did not testify at trial, his counsel stipulated at the evidentiary hearing
that Trenkler had built the Quincy bomb.

1986 Quincy Bomb

Trenkler constructed the Quincy bomb in 1986 for a friend, Donna Shea.
At the time, Shea was involved in a dispute with the owners of the Capeway
Fish Market and she wanted the bomb to use as a means to intimidate them.
At her request, Trenkler assembled a remote-control, radio-activated explosive
device. The device was later attached to the undercarriage of a truck
belonging to the Capeway Fish Market and detonated in the middle of the
night. The resulting bomb blast caused no injuries and little property
damage.

In building the Quincy bomb, Trenkler used as the explosive material
a military flash simulator typically utilized to mimic gunfire in combat
exercises. To provide remote-control capabilities, Trenkler employed a
radio-receiver he had removed from a small toy car. Trenkler wrapped the
bomb in duct tape and attached a large donut-shaped speaker magnet to
enable the bomb to adhere to the undercarriage of the truck. Other components
Trenkler used included a "double throw" toggle switch, four AA batteries,
two six-volt batteries, an electric relay, solder, various wires, and
a slide switch.

Testimony at trial established that Trenkler purchased some of the electrical
components for the Quincy bomb from a Radio Shack store. On one occasion,
Trenkler sought to obtain needed components by sending Shea's eleven-year-old
nephew into a Radio Shack store with a list of items to purchase while
Trenkler remained waiting outside. Shea's nephew, however, was unable
to find all of the items, and Trenkler eventually came into the store
to assist him.

1991 Roslindale Bomb

The government contended that Trenkler built the Roslindale bomb at Shay
Jr.'s request. At trial, the government offered evidence about Trenkler's
relationship with Shay Jr., dating back at least two years prior to the
Roslindale bombing. Several witnesses, including Trenkler's business partner,
reported seeing the two together on different occasions in 1990 and 1991.
Shay Jr.'s address book included an entry for Trenkler listing his current
pager number. Moreover, Trenkler's roommate at the time of the Roslindale
bombing testified that, during September and October of 1991, Shay Jr.
left several voice-mail messages on the pager for Trenkler.

Testimony from government investigators and Shay Sr. established that
the Roslindale bomb was a remote-control, radio-activated device with
an explosive force supplied by two or three sticks of dynamite connected
to two electrical blasting caps. A black wooden box weighing two or three
pounds and measuring approximately eight- to ten-inches long, five- to
six-inches wide and one- to two-inches deep housed the bomb. A large donut-shaped
magnet and several smaller round magnets attached to the box were used
to secure the device to the underside of Shay Sr.'s automobile. Other
components used in the construction of the bomb included duct tape, a
"single throw" toggle switch, four AA batteries, five nine-volt batteries,
a Futaba radio receiver, solder, various wires, and a slide switch.

According to the government's experts and Shay Sr., the bomb was originally
attached to the undercarriage of Shay Sr.'s automobile directly beneath
the driver's seat. The government's explosives expert testified that if
the bomb had exploded while still attached to the car, it probably would
have killed or at least seriously injured any individual sitting in the
driver's seat.

The government also asserted that Trenkler used Shay Jr. to purchase
the electronic components used in the bomb. In support of this assertion,
the government introduced a sales receipt for a toggle switch purchased
in October 1991 at a Radio Shack store located across the street from
where Trenkler, at the time, was installing a satellite dish. Agents from
the Bureau of Alcohol, Tobacco and Firearms ("ATF") recovered from the
debris of the Roslindale bomb a switch identical to the one purchased.
Shay Jr. admitted purchasing the switch during a taped television interview,
portions of which the government introduced at trial. Furthermore, a sales
clerk at the Radio Shack testified that, prior to purchasing the switch,
the person who bought it had browsed in the store for several minutes,
appearing to shop for items written on a list. The sales clerk also testified
that he recalled seeing Trenkler in the store on two or three occasions
during the fall of 1991.

Both the government and Trenkler elicited testimony from their respective
explosives experts explaining the similarities and differences between
the two bombs. Both experts testified at length concerning the electronic
designs, the choice of components and the method of construction. The
government's expert opined that the two incidents shared many similar
traits and characteristics, evincing the "signature" of a single bomb
maker. He further stated that he had no doubt "whatsoever" that the same
person built both bombs. Trenkler's expert, on the other hand, stated
that too many dissimilarities existed to conclude that the same person
built both bombs. Moreover, Trenkler's expert testified that the similarities
that existed lacked sufficient distinguishing qualities to identify the
two bombs as the handiwork of a specific individual.

EXIS Computer Database Evidence

To support the inference that Trenkler built both bombs, the government
offered testimony both at the pretrial hearing and at trial concerning
information retrieved from an ATF computer database of explosives and
arson incidents. Stephen Scheid, an Intelligence Research Specialist with
ATF, testified that the database, known as EXIS, contains information
taken from reports submitted to ATF by various federal, state and local
law-enforcement agencies. Scheid further testified that he had been personally
responsible for maintaining the database since 1977. Scheid stated that
he reviews submitted incident reports, culling from them information describing
the characteristics of each bombing or arson episode. Scheid added that
he then encodes the extracted information on a standardized worksheet,
which he or a data-entry person in turn uses to enter the information
into the database.

Scheid testified that, through the use of a computer program, he then
produces investigatory leads by retrieving all incidents entered in the
database that are listed as possessing a specific component or characteristic.
Scheid further testified that, in an effort to identify the builder of
the Roslindale bomb, he performed a series of computer queries, focusing
on characteristics of the Roslindale bomb. This series of inquiries narrowed
the field of reported incidents in the database from 40,867 to seven.
(2)

The seven remaining incidents included both the Roslindale and Quincy
bombs. Scheid stated that he subsequently conducted a manual analysis
of the remaining incidents and was able to identify several additional
characteristics common to only the Roslindale and Quincy bombs.

Scheid also testified that the report of the Quincy bomb did not come
to his attention through normal procedures. Scheid did not receive information
about the 1986 Quincy bomb, nor enter any information pertaining to it
into the EXIS database, until after the Roslindale incident in 1991.

The jury returned a guilty verdict on all counts of the indictment. Subsequently,
the district court sentenced Trenkler to concurrent terms of life imprisonment
on the counts of receipt of explosive materials and attempted malicious
destruction of property by means of explosives and sixty months on the
count of conspiracy. Trenkler now appeals.

II.

Discussion

On appeal, Trenkler assigns error to the admission of the Quincy bomb
evidence, contending primarily that the incident was not sufficiently
similar to the Roslindale bomb to be relevant on the issue of identity,
and to the admission of the EXIS database-derived evidence that the government
used to prove the similarity of the two bombs. ...

A. Quincy Bombing Evidence

We begin with Trenkler's contention that the district court erred in
admitting the evidence of the Quincy bombing.

1. Fed. R. Evid. 404(b): Other Act Evidence

In general, Rule 404(b) n11 proscribes the use of other bad-act evidence
solely to establish that the defendant has a propensity towards criminal
behavior. Rule 404(b)'s proscription, however, is not absolute: the rule
permits the use of such evidence if it bears on a material issue such
as motive, knowledge or identity. In this Circuit, we have adopted a two-part
test for determining the admissibility of Rule 404(b) evidence. E.g.,
United States v. Williams, 985 F.2d 634, 637 (1st Cir. 1993). First, the
district court must determine whether the evidence has some "special relevance"
independent of its tendency simply to show criminal propensity. E.g.,
United States v. Guyon, 27 F.3d 723, 728 (1st Cir. 1994). Second, if the
evidence has "special relevance" on a material issue, the court must then
carefully conduct a Rule 403 analysis to determine if the probative value
of the evidence is not substantially outweighed by the danger of unfair
prejudice. ..... As with most evidentiary rulings, the district court
has considerable leeway in determining whether to admit or exclude Rule
404(b) evidence. Accordingly, we review its decision only under the lens
of abuse of discretion. ...

2. Identity

The government offered the evidence of the Quincy bomb, which Trenkler
admitted building, primarily to prove that Trenkler also built the Roslindale
bomb. The government contends that the evidence of the Quincy bomb has
"special relevance" on the issue of identity because the numerous similarities
surrounding the Quincy and Roslindale incidents compel the conclusion
that the same individual built both bombs. Trenkler, on the other hand,
argues that the Quincy incident is too dissimilar to be relevant on the
issue of identity, and even if it has some relevance, the risk of unfair
prejudice that it poses far outweighs its probative value. We agree with
the government that the Quincy bomb evidence has "special relevance" on
the issue of identity and that the district court did not abuse its considerable
discretion in admitting it.

a. Rule 404(b) Evidence: Special Relevance

When, as in this case, Rule 404(b) evidence is offered because it has
"special relevance" on the issue of identity, we have required, as a prerequisite
to admission, a showing that there exists a high degree of similarity
between the other act and the charged crime. ... Indeed, the proponent
must demonstrate that the two acts exhibit a commonality of distinguishing
features sufficient to earmark them as the handiwork of the same individual.
... This preliminary showing is necessary because

[a] defendant cannot be identified as the perpetrator of the charged
act simply because he has at other times committed the same commonplace
variety of criminal act except by reference to the forbidden inference
of propensity. The question for the court[, therefore, must be] whether
the characteristics relied upon are sufficiently idiosyncratic to permit
an inference of pattern for purposes of proof.

Resolving whether the prior act is sufficiently similar to the charged
offense to have "special relevance" on the issue of identity, however,
is essentially an issue of "preliminary" or "conditional" fact. In other
words, the prior act has no tendency to prove the perpetrator's identity-i.e.,
it is not relevant -- unless the proponent can first establish the conditional
fact: that the two acts are sufficiently idiosyncratic to support the
inference that they are the handiwork of the same individual. The admissibility
of evidence whose relevance turns on the resolution of a conditional fact
is governed by Fed. R. Evid. 104(b). See Huddleston v. United States,
485 U.S. 681, 689, 99 L. Ed. 2d 771, 108 S. Ct. 1496 (1988). ...Moreover,
in determining whether the Government has introduced sufficient evidence
to meet Rule 104(b), the trial court neither weighs credibility nor makes
a finding that the Government has proved the conditional fact by a preponderance
of the evidence. The court simply examines all the evidence in the case
and decides whether the jury could reasonably find the conditional fact
. . . by a preponderance of the evidence. Huddleston, 485 U.S. at 690.
Thus, as here, when a party seeks to admit Rule 404(b) evidence to establish
identity, the district court must condition its admission on a showing
that the shared characteristics of the other act and the charged offense
are sufficiently idiosyncratic that a reasonable jury could find it more
likely than not that the same person performed them both.

Trenkler contends that the array of similarities between the two incidents
amounts to no more than a collection of "prosaic commonalit[ies that]
cannot give rise to an inference that the same person was involved in
both acts without reference to propensity." United States v. Garcia-Rosa,
876 F.2d 209, 225 (1st Cir. 1989), .... However, in resolving whether
the evidence supports an inference that the two incidents are "sufficiently
idiosyncratic," we have cautioned that "an exact match is not necessary."
.... The test must focus on the "totality of the comparison," demanding
not a "facsimile or exact replica" but rather the "'conjunction of several
identifying characteristics or the presence of some highly distinctive
quality.'" .....In this case, we think the balance of the evidence tilts
sufficiently towards admission to satisfy the first step of the Rule 404(b)
analysis. Accordingly, we believe that the district court did not abuse
its discretion in determining that the numerous similarities in components,
design, and technique of assembly, combined with the similar modus operandi
and the closeness of geographic proximity between the two events, sufficiently
support the inference that the same person built both bombs.

We begin by noting that the government's explosives expert, Thomas Waskom,
testified that his analysis of the similarities shared by the two incidents
left him with no doubt "whatsoever" that the same individual built both
bombs. Our own review of the record reveals that the two bombs did indeed
share a number of similar components and characteristics. Both bombs were
remote-controlled, radio-activated, electronic explosive devices. Both
were homemade mechanisms, comprising, in general, electronic components
easily purchased at a hobby store. Both had similar, though not identical,
firing and fusing circuits with separate battery power supplies for each.
Both had switches in their fusing circuits to disconnect the radio receivers.
To energize their respective radio receivers, both devices utilized similar
power supplies, consisting of four AA batteries. Both employed many similar
components such as batteries, duct tape, toggle switches, radio receivers,
antennas, solder, electrical tape, and large round speaker magnets. Moreover,
both used a distinctive method (i.e., twisting, soldering, and taping)
to connect some, though not all, of the wires used. Though we hardly find
any of these factors by themselves to be "highly distinctive," the coalescence
of them is fairly persuasive. Indeed, even Trenkler's expert witness,
Denny Kline, testified at the pretrial hearing that, in light of these
similarities, "there is a possibility, a probability, that maybe there
is a connection between the maker of these two bombs." (Emphasis added.)

Accordingly, we believe some significance is properly attributed to the
simple fact that both incidents are bombings. A bombing, in and of itself,
is, arguably, a fairly distinctive method for intimidating or killing
an individual..... In addition, both incidents involved not simply bombs,
but remote-control bombs that were placed underneath automotive vehicles.

In both instances, the bombs were constructed and used to benefit a friend
of the builder. Trenkler built the Quincy bomb for Donna Shea to use to
intimidate the owners of the Capeway Fish Market, and the evidence supported
the inference that the person who constructed the Roslindale bomb built
it for Shay Jr. to use against his father. Furthermore, in both instances
the builder attempted to conceal his or her participation by using a third
party to purchase the electronic components used in the explosive device.
In 1986, Trenkler initially waited in his car while sending Donna Shea's
nephew into the electronics store with a list to purchase the needed components.
Similarly, the evidence supports the inference that the builder of the
Roslindale bomb used Shay Jr. to purchase the needed components. Finally,
the fact that both bombings occurred within a relatively close geographic
proximity must be given some weight in the analysis.

In United States v. Pisari, 636 F.2d 855 (1st Cir. 1981), we reversed
the district court's decision to admit evidence of a prior robbery solely
on the issue of identity, where the only similarity between it and the
charged offense was that a knife was used. Similarly, in Garcia-Rosa,
876 F.2d at 224-25, we refused to sanction the admission of a prior drug
transaction where the only characteristic linking it to the charged drug
deal was the characteristic exchange of a sample of drugs prior to the
sale. In Garcia-Rosa, we held that a single "prosaic commonality" was
insufficient "to give rise to an inference that the same person was involved
in both acts without reference to propensity." Id. at 225. See also United
States v. Benedetto, 571 F.2d 1246, 1249 (2d Cir. 1978) (no signature
where shared characteristic is merely "a similar technique for receiving
the cash: the passing of folded bills by way of a handshake").

In the present case, however, the government presented more than a single
"prosaic commonality." Indeed, the government propounded a laundry list
of similarities in design, component selection, construction and overall
modus operandi. On the other hand, Trenkler offered a fairly impressive
list of differences between the two incidents. In the absence of one or
more highly distinctive factors that in themselves point to idiosyncracy,
we must examine the combination of all the factors. Had Trenkler been
unable to point to any significant differences, we suspect he would have
had little chance in establishing an abuse of discretion in allowing the
evidence. Similarly, had the government found but three or four common
characteristics to establish sufficient similarity, we doubt that the
admission of the evidence would have been granted or sustained. Here,
in the middle, with substantial evidence on either side and conflicting
expert opinions, could a reasonable jury have found it more likely than
not that the same person was responsible for both bombs? We think the
answer is yes. ...

b. Rule 404(b) Evidence: Probative Value and Unfair Prejudice

Resolving that the district court did not abuse its discretion in determining
that a rational jury could infer that it was more likely than not that
the same person built both bombs, however, does not end the analysis.
We must also review the trial court's determination that the probative
value of the evidence was not substantially outweighed by the risk of
unfair prejudice. Several factors weigh heavily in this balancing, such
as the government's need for the evidence, ..., the strength of evidence
establishing the similarity of the two acts, ..., the inflammatory nature
of the evidence, and the degree to which it would promote an inference
based solely on the defendant's criminal propensity, ....

We believe the district court acted well within its broad discretion
in admitting the evidence. First, the evidence was important to the government's
case. The evidence that Trenkler had built the Quincy bomb corroborated
David Lindholm's testimony, identifying Trenkler as the builder of the
Roslindale bomb. Second, although the evidence of similarity could have
been more compelling, it was nonetheless substantial: Indeed, the government's
explosives expert testified that he had no doubt "whatsoever" that the
same person designed and constructed both bombs.

On the other hand, we disagree with the district court that the evidence
did not pose any risk of unfair prejudice. As with all "bad act" evidence,
there is always some danger that the jury will use the evidence not on
the narrow point for which it is offered but rather to infer that the
defendant has a propensity towards criminal behavior. Nonetheless, outside
the context of propensity, the evidence was not unduly inflammatory. The
Quincy bomb did not kill or injure any individual and caused little property
damage. Moreover, the district court minimized any risk of unfair prejudice
by carefully instructing the jury not to use the evidence of the Quincy
bombing to infer Trenkler's guilt simply because he was a bad person or
because the fact he had a built a bomb in the past made it more likely
he had built the bomb in this case. In sum, we believe that the district
court did not abuse its discretion in determining that the probative value
of the Quincy bomb evidence was not substantially outweighed by the risk
of unfair prejudice. (3)

....

For the foregoing reasons, we affirm Trenkler's conviction.

TORRUELLA, Chief Judge, (Dissenting). In my view, the
erroneous admission in this case of evidence derived from the EXIS computer
database violated the defendant's Sixth Amendment right to confront witnesses
against him. Contrary to my brethren, I do not believe that this error
was harmless beyond a reasonable doubt. I therefore dissent.

I.

....

The majority also alludes to a potentially more pernicious problem concerning
the EXIS-derived evidence. The majority notes that the database entry
for the Roslindale incident lists approximately twenty-two characteristics
describing that incident, but Scheid, inexplicably, chose only to query
ten of those characteristics. (4)... The majority notes that there is
nothing to suggest that these ten characteristics are more important to
a bomb-signature analysis than any of the other characteristics not chosen.
Scheid offers no reason why he chose to query only certain generic characteristics
instead of the more specific characteristics of the Roslindale bomb, which
would be more evincing of a "signature." For example, the Quincy device
would not have been a match if Scheid had queried any of the following
characteristics of the Roslindale bombing: Futaba antenna, Rockstar detonator,
use of dynamite, nails, glue, 6-volt battery, slide switch, paint, magazine
page, or black electrical tape. The majority leaves the implication unspoken.
I will not be so discreet. The obvious implication is that Scheid chose
the particular characteristics in an attempt to find a match with the
Quincy device. This implication is enforced by the fact that, according
to Scheid's own testimony, the Quincy incident was not entered into the
database until after the Roslindale incident. That is, government agents
brought the Quincy bombing to Scheid's attention when they asked him to
investigate the Roslindale bombing.

....

As I see it, there are three related reasons why admission of the EXIS
evidence cannot be considered harmless beyond a reasonable doubt. First,
it is clear to me that the district court relied on the improper EXIS
evidence in its decision to allow the government to present evidence of
the Quincy incident to the jury to prove identity under Rule 404(b).

At the hearing on its motion in limine to admit evidence of the Quincy
incident under Fed. R. Evid. 404(b), the government presented the testimony
of Scheid, regarding the EXIS computer analysis, and the testimony of
the government's bomb expert, Waskom, who testified that, in his opinion,
the Quincy and Roslindale devices were so similar that they must have
been built by the same person. In turn, Trenkler presented expert testimony
that the devices were too different for anyone to be able to determine
if they were built by the same person. After hearing this evidence, the
district court concluded that "the similarities [between the two incidents]
are sufficient to admit the evidence under the rules established . . .
by the First Circuit."

The majority states that, based upon its review of the record, it is
convinced that the EXIS-based evidence "was not a critical factor in the
district [**66] court's decision to admit the Quincy bomb evidence for
purposes of identity. The EXIS-derived evidence was merely cumulative,
corroborating the testimony of the government's explosives expert." Supra
pp. 39-40. Yet the record demonstrates that the district court judge thought
otherwise when she decided to admit evidence of the 1986 Quincy incident.
In her oral opinion on the government's motion, the district court judge
began by summarizing the testimony of Waskom, and then stated: "Adding
to this evidence, the statistical evidence from the EXIS system, I am
persuaded that the two devices are sufficiently similar to prove that
the same person built them, and thus relevant to the issues in this case."
(emphasis added). The district court judge did not say that the EXIS evidence
"corroborated" Waskom's testimony. She stated that, when she adds the
EXIS evidence to Waskom's testimony, she becomes convinced that the two
devices are sufficiently similar. It is plain that the district court
judge relied on the EXIS evidence to form the critical final link between
the two devices. Indeed, in arguing its motion, the government chose to
first present the EXIS evidence and then to present the Waskom testimony,
suggesting that it intended the latter to corroborate the former. The
district court's erroneous determination that the EXIS evidence was admissible
led not only to the jury hearing that evidence, but also to the jury hearing
Waskom's testimony with respect to the two incidents. I cannot agree,
therefore, that admission of this evidence was harmless beyond a reasonable
doubt.

The second reason that admission of the EXIS evidence cannot be considered
harmless is that this type of "scientific" evidence is too misleading,
too powerful, and has too great a potential impact on lay jurors, to be
disregarded as harmless.

The EXIS-derived evidence was, in the best case scenario, unintentionally
misleading, and, in the worst case scenario, deliberately skewed. Scheid
testified that, in entering information about the Quincy incident into
the EXIS database, he relied solely on a laboratory report prepared in
1986 by investigators from the Massachusetts Department of Public Safety.
This report does not state that the Quincy device was attached to the
underside of the Capeway truck. Rather, it refers only to an "explosion
on truck." Somebody must have given Scheid further information about the
Quincy explosion because he entered "under vehicle" as a characteristic
of the Quincy incident. The majority acknowledges these facts but, inexplicably,
makes no comment. See supra n.8. These facts are important for three reasons.
First, they illustrate the fallibility of the underlying reports. How
many of the other 14,232 reports had similar defects? Second, they illustrate
how easily one wrong or incomplete entry can affect a query result. If
Scheid had actually followed the report, the Quincy incident would not
have matched the Roslindale bombing because Scheid's query entry was for
a bomb "under vehicle." Finally, these facts indicate that the EXIS test
was skewed (whether intentionally or unintentionally) to find a match
between the Quincy and Roslindale incidents.

The EXIS-derived evidence is also misleading because it focuses the jury's
attention on the trees instead of the forest. By focusing on similar minor
aspects between the two devices -- e.g., duct tape, magnets and soldering
-- the majority completely brushes aside the fact that the central and
most important ingredient in the two devices is fundamentally different.
The central ingredient in a bomb, one would think, is the explosive content
(in much the same way that the central ingredient in a high-performance
car is the engine). The Roslindale bomb used two to three sticks of dynamite
-- a very powerful explosive. The Quincy device used an M-21 Hoffman artillery
simulator, which is a device used by the military to simulate, in a safe
fashion, the flash and noise of artillery. The simulator is, in effect,
a firecracker-like device; it has no where near the strength of dynamite.
In stark contrast to dynamite, a simulator is not designed to cause physical
or property damage. Indeed, while the Roslindale device created an explosion
large enough to kill, the Quincy device caused no visible damage to the
truck it was placed under. Equating the two devices is like equating a
BB gun with a high caliber rifle.

The misleading nature of the EXIS-derived statement is compounded by
the nature of its source, and the way in which it was presented to the
jury. Not only is it rank hearsay evidence, it is hearsay evidence wrapped
in a shroud of "scientific" authenticity. This is not a paid government
expert testifying that, in his opinion, the two devices were built by
the same person; this is a computer declaring that the two devices were
built by the same person. Computers deal in facts, not opinions. Computers
are not paid by one side to testify. Computers do not have prejudices.
And computers are not subject to cross-examination. Moreover, the chart
of the EXIS queries performed by Scheid, and the printouts of the results
of those queries, were introduced into evidence and presented as exhibits
to the jury. Consequently, the jury had this misleading, physical evidence
with them in the jury room during deliberations. Does it not stand to
reason that the lay juror will accord greater weight to a computer's written
findings than to the testimony of a government expert witness? The common-sense
answer is, of course.

....

V.

A horrible crime was committed in which one police officer was killed
and another seriously injured. Society rightfully demands that the guilty
be apprehended, tried, and punished. But the distinguishing feature of
our legal system is that even those charged with grotesque crimes are
guaranteed certain constitutional rights intended to ensure that they
receive a fair trial. Unfortunately, and with all due respect to my brethren,
I believe the defendant's right to a fair trial was violated when the
government was permitted to introduce the highly prejudicial evidence
derived from the EXIS computer database. Because this error so severely
violated defendant's Sixth Amendment right to confront the witnesses against
him, and because the remainder of the evidence against him was not "overwhelming,"
I dissent.

Do you agree that the defendant's modus operandi was a sufficiently
distinctive method of making bombs as to rise to a level of "signature
quality" identity evidence? What about the role of the computer to "match"
the two incidents? Isn't it always possible to select several features
of any activity that are likely be the similar when the activity is repeated,
even by different actors? Which attributes, either alone, or in conjunction
with others, are really as unique as a "signature"?

An interesting variation on this problem occurs when a defendant attempts
to introduce evidence of other similar crimes by someone else to prove
that the case on trial is a case of mistaken identity. The Colorado Supreme
Court has adopted the position that similar offense evidence when introduced
by the defendant is subject to a case-by-case test of admissibility. People
v. Flowers, 644 P.2d 917 (Colo. 1981). In Flowers, defendant
was convicted of first-degree sexual assault and sought to introduce evidence
of nine other sexual assaults in the same locality within five months
of his alleged assault. The defendant wanted to offer testimony from detectives
that each of the victims was unable to identify the defendant from a line-up
as her assailant and to call a forensic serologist to testify that seminal
fluid recovered from one of the sexual assault victims excluded the defendant
as the assailant. The court upheld the district court's determination
that the details of the other crimes were not distinctive enough to represent
the "signature" of a single individual but were features common to most
sexual assaults.

It is interesting to note the nonsymmetrical application of the Rule
403/404 two-step approach. For example, in Flowers if the semen
had matched and the defendant had been positively identified for one of
the prior neighborhood assault cases, such evidence might have been admitted
if the government could point to some "unique" characteristics shared
by the assaults.

If the two-step approach is to be applied nonsymmetrically when evidence
of other crimes is offered exculpatorily by the defendant, which way should
the scales of admissibility tilt?